p 0 v 2 study in s NN = 200GeV Au+Au collisions

Masashi Kaneta, RBRC, BNL Heavy Ion Tea in Nuclear Science Division, LBNL (2003/11/5) 1

KANETA, Masashi

for the PHENIX Collaboration

RIKEN-BNL Research Center

00 v v22 study studyin in ssNNNN = 200GeV = 200GeV Au+Au collisionsAu+Au collisions


Why Event Anisotropy?Why Event Anisotropy?

• Because of sensitive to collision geometry– In low pT (~<2 GeV/c)

• Pressure gradient of early stage• Hydrodynamical picture is established

– In high pT (>~2 GeV/c)• Energy loss in dense medium (Jet Quenching)• Partonic flow(?)

x

zy

Here we focus onellipticity of azimuthalmomentum distribution, v2 (second Fourier coefficient)


PHENIX ExperimentPHENIX Experiment• Lead Scintillator and Lead Glass

EMCs – Gamma measurement (0)

• BBCs and ZDCs– Collision centrality determination

• BBCs– Reaction plane determination and– Its resolution correction


BBC in PHENIXBBC in PHENIX

NorthSouth

144.35 cm

⊿η = 3.1 ~ 4.0

⊿φ = 2π

64 elements

Quartz Cherenkov radiator

meshed dynode PMT

• inner ring• middle ring• outer ring

BBC


PbGl and PbSc EMC’sPbGl and PbSc EMC’s

• 1 Sector = 6x3 Supermodules (SM)• 1 PbSc SM = 12x12 towers• PbSc towers: 5.52 x 5.52 x 33 cm3 (18 X0)• 15552 blocks total

1 PbSc tower: • 66 sampling cells• 1.5 mm Pb, 4 mm Sc• Ganged together by penetrating wavelength shifting fibers for light collection• Readout: FEU115M phototubes

• 2 Sectors PbGl

• 1 PbGl Sector• 16x12 supermodules (SM)

• 1 PbGl SM• 6x4 towers • Separate reference system

• 1 FEM • Reads out 2x3 supermodules or 12x12 towers


Method of Method of 00 v v22 Measurement Measurement

• Define reaction plane by charged multiplicity on Beam-Beam Counters

• 0 reconstruction from gamma measured by Electro-Magnetic Calorimeter (EMC)• For each pT, azimuthal angle, centrality

• Combine both information– Counting number of 0 as a function of

]cos[ 21 2

1

1

2

3

3

rn

measuredn

TT

nvdydpp

Nd

pd

dNE

,....3,2,1 where n

event anisotropy parameter measured

azimuthal angle of the particlereaction plane angle

vnreal = vn

measured/ (reaction plane resolution)n

Note: the detail of reaction plane definition will be found in nucl-ex/0305013


Reaction Plane Defined by Reaction Plane Defined by BBC’sBBC’s

• BBC north and south (~3-4) are used

• Resolution calculation– Two sub-events are selected– North and south

- /2 /2-

/2

/2 Correlation of two BBC’s


00 Identification Identification

• Requirement for photon– Dead and noisy EMC towers are removed for the analysis– Energy of shower on EMC>0.040 [GeV]– PID cuts: 2<3 for photon probability– |TOF|<1.2 [ns]

– Note: those cut are loser than single pT distribution analysis

• For 0

– Asymmetry cut: |E1–E2| / ( E1+E2) < 0.8

– Combinatorial background is estimated by event mixing• Classes categorized for event mixing

– centrality : every 10%– BBC Z Vertex : every 10cm in ±30cm– reaction plane direction in PHENIX detector : 24 bins in ±


Example Plots from the Analysis ProcedureExample Plots from the Analysis Procedure

Invariant mass of from same event and mixed event (classed by reaction plane, centrality, vertex position)

normalization rangefor combinatorial B.G.subtraction

After subtraction, there is 2nd component of B.G. in pT<2GeV/c region

shape assumed aslinear+asym. Gauss

count number of 0 in a rangeafter 2nd B.G. subtraction(not used the fit function)

m [GeV/c2]

200GeV Au+Au

m

[GeV/c2]

R [rad]

Fit function:(average of 0 count) ( 1 + 2 v2 cos[2( - R)])

Green lines : deviation by error of v2


One of difficulties (?) is..One of difficulties (?) is..

• The analysis of v2

– Counting number of 0 as a function of centrality, pT and -R

– The analyses (fitting of combinatorial background, its

subtraction, counting 0 and so on) are done by macro automatically

– However, we need to think it is not perfect, that is, it may fail sometime

• Therefore, ....


Toooooooooo many histograms checked by Toooooooooo many histograms checked by eyeseyes

After combinatorial background subtraction

Example of invariant mass distributions for each pT, -R in a centrality bin

Before combinatorial background subtraction 0 as a functionof Rb


vv22 vs. p vs. pT T vs. Centrality from 200GeV vs. Centrality from 200GeV

Au+AuAu+AuStatistical error is shown by error bar

Systematic error from 0 count method and reaction plane determination is shown by gray box

phenix preliminary


}nucl-ex/0305013

phenix preliminary

vv22 vs. p vs. pT T vs. Centrality from 200GeV vs. Centrality from 200GeV

Au+AuAu+AuStatistical error is shown by error bar

Systematic error from 0 count method and reaction plane determination is shown by gray box

• Charged +K v2 consistent with 0 v2 in pT<4GeV/c

The charged and K v2 are shown only with statistical errors


phenix preliminary

vv22 vs. p vs. pTT (Minimum Bias) from 200GeV (Minimum Bias) from 200GeV

Au+AuAu+Au

• Identified particle v2 up to pT=10GeV/c

36.3106 [events] = 5.3+0.5-0.4 [(b)-1]


}nucl-ex/0305013

phenix preliminary


Au+AuAu+Au


36.3106 [events] = 5.3+0.5-0.4 [(b)-1]


phenix preliminary

nucl-ex/0305013


Au+AuAu+Au


36.3106 [events] = 5.3+0.5-0.4 [(b)-1]


Comparison with KComparison with K00SS and and (STAR) (STAR)

STAR data fromnucl-ex/0306008


Quark Coalescence?Quark Coalescence?• Phys. Rev. Lett. 91 (2003) 092301, D.Molnar and S.A. Voloshin

• qqmeson, qqq(qqq)Baryon

• How data looks like?

- - - -

• Non-strange and strange meson and baryon seems to be merged around pT/nquark 1-3GeV/c

• But we need more statistics to conclude it


Comparison with a modelComparison with a model

phenix preliminary

Hydrodynamical calculation agreed in pT~<2 GeV/c. After that, it is deviated.

Hydrodynamical calculation


Comparison with a model which is described in nucl-th/0306027. Here we don't want to discuss which model can describe the data. To conclude which model can describe the data, we need much more statistics in high pT region.

Special thanks toC. Nonaka (one of authors)of nucl-th/0306027 fordata of model calculation

Comparison with a modelComparison with a model

phenix preliminary


SummarySummary

• First measurement of 0 v2 at RHIC– In pT=1-10 GeV/c– v2 of the highest pT from identified particle

• Charged v2 consistent with 0 v2

– In pT=1-3GeV/c

• Minimum bias data shows finite 0 v2 – Up to pT~8 GeV/c

Special thanks to LBL and STAR people, especially Art Poskanzer

– I learned all of event anisotropy analysis when I was here


OutlookOutlook

• Feature plan of analysis– Using high pT gamma trigger in run2 Au+Au data

• We will have about twice statistics in high pT

• need to study trigger bias– therefore, present analysis results are from minimum bias trigger

events

– v2 is also available by same method

– PHENIX has photon v2 also (STAR also, but not opened yet)

– photon v2, especially low pT!

• RHIC run4 Au+Au, it will be– Much more statistics

• Detail study of v2 shape around pT=2-4GeV/c

– Much higher pT

• We want to know where is the end of finite v2 in very high pT


Future Plan of Event Anisotropy Analysis in Future Plan of Event Anisotropy Analysis in PHENIX PHENIX

• Trying v2 for all of possible particles with large statistics– Already tried

• charged ,K,p, deuteron, 0, e+(-) (inclusive), gamma (inclusive)– On going but need much more statistics

• eta• direct gamma

– inclusive gamma – [contribution from 0, eta (dominantly)]• charm and bottom meson

– inclusive e+(-) – [contribution from 0 and eta dalitz decay (dominantly)]

– Seems to be hard work, but...• K0

s

• Lambda• resonances• penta-quark

• v1 on BBC (=3-4)• Correlation method for vn

• Cross section and HBT radii in-plane and out-plane


Electron and Positron vElectron and Positron v22

pT[GeV/c]

v 2

From talk ofSingo Sakai (Ph.D student at Tsukuba Univ.)at JPS autumn meeting 2003 and DNP2003

PHENIX preliminary

200 GeV Au+Au Min. Bias


Photon vPhoton v22

PHENIX preliminary

200 GeV Au+Au Min. Bias

STAR from my analysis(not finished...)

v 2

pT [GeV/c]

From DNP2003 talkSaskia Mioduszewski,Edouard Kistenev, andShinIchi Esumi

p 0 v 2 study in s NN = 200GeV Au+Au collisions

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